There is known a packaging bag which is provided with a spout assembly at the upper portion of a bag body. In general, such a packaging bag, provided with the spout assembly, has an inner content to be discharged through the spout assembly by grasping and crushing the bag body with a hand to thereby increase an inner pressure and take out the inner content, or sucking the inner content through the mouth portion of the spout assembly.
In a developed art, the packaging bag with the spout assembly is provided with a valve body which permits an inner content to flow out from the bag body only where a predetermined condition is satisfied.
For example, in a Patent Publication 1, there is shown a packaging bag in which, in order to prevent air from invading inside the bag body through the spout assembly, a valve body formed of an elastic material such as rubber is attached to a bag body side in the axial direction of the spout assembly. Such a valve body is formed from a relatively thin plate-shaped elastic material and provided with a cross-shaped cut-in penetrating the elastic material in its thickness direction.
According to such a valve body, when the bag body is grasped and crushed, the inner pressure increases and the cut-in portion is opened toward an opening side by the inner content pushed by the hand, thus ensuring an inner content flow-out path. When the grasping pressure is weakened, the inner pressure is decreased and the opened cut-in portion is returned to the original shape by its self resilient force, and the valve body is hence closed. In the packaging bag provided with the spout assembly disclosed in the Patent Publication 1, the inner content is discharged through such operations as mentioned above and the air invasion into the bag body is also prevented through such operations.
On the other hand, Patent Publication 2 discloses an invention of a packaging bag provided with a spout assembly, which is provided with a check valve, inside the spout assembly, permitting an inner content to flow only to the bag body side from the mouth side of the spout assembly.
The check valve provided for this packaging bag with the spout assembly includes a valve body moving along the axial direction of the spout assembly, an urging member urging the valve body from the bag body side toward the mouth side, and a valve seat formed inside the spout assembly and having a central flow-passage.
According to the check valve, when an aspirated air is introduced inside the spout assembly from outside, the aspirated air pushes down the valve body against the urging force, thereby ensuring the flow-passage. Thus, the aspirated air enters inside the bag body. On the contrary, when the introduction of the aspirated air form the outside stops, the valve body urged by the urging member abuts against the valve seat to thereby close the flow-passage and shut off the flowing inside the spout assembly. Therefore, the aspirated air flowing into the bag body is prevented from flowing outside the packaging bag.
Patent Publication 1: Japanese Patent Unexamined Application Publication No. 2004-59071.
Patent Publication 2: Japanese Patent Unexamined Application Publication No. 2000-168806.